Audio De-Syncing

Q: Do you know why the sound keeps going more and more out of sync on my computer as I play a video file? I downloaded the latest codec packs, which made no difference. But when I switch my surround-sound system off and then back on again, the audio track goes back into syncbefore gradually losing sync again. Pressing the function button and going though the different functions and back to the digital input also temporarily fixes the problem, but then the audio drifts out of sync once more. I have a Trust SC-5250 5.1 Surround Sound card. Could it be the drivers for this component, or could it be my surround-sound system?

I have a Samsung DVD Home Theatre System that works fine when I play DVDs or when I am playing an AVI file from a USB stick. Are there separate codecs for the surround sound? Or is there firmware that needs updating?Adam Love

A: Losing sync between voice and video is an annoying problem. It's also something that can crop up if you play console or PC games in this type of environmentand it's a tricky one to solve, because there are multiple potential causes in the video chain, though the root causes are similar.

Modern A/V devices (including HDTV displays, many new-generation LCD monitors, and A/V receivers) cause delays in video, but not so much in audio. This is because of the video processors built into those devices. Upscaling or other video processing (ranging from 3:2 pulldown and anti-aliasing to edge enhancement and others) can delay the journey of video onto your monitor. These delays are typically on the order of milliseconds, but if a device doesn't do the same for audio, then the audio for a particular frame of video can arrive before the correct video frame.

In games, this can mean your game controller button pushes don't register "fast enough," even though you are pressing those buttons at the correct time. The symptom is different, but the cause is the same.

Curing the problem can be difficult. Some displays actually have controls allowing you to sync up audio and video; others don't. In those cases, the only way to fix the problem is to disable all video processingbut then image quality can suffer. Also, you need to be aware of where in the processing chain the delays occur. Is it in the monitor? The A/V receiver? The source device? You need to check all elements. On displays, this is done with the video controls embedded in the on-screen menu. Similarly, you can control A/V receivers connected to a display with the on-screen menu, though some receivers have a large enough LED display for you to make the changes using the remote control.

HDMI 1.3 has a new feature known as "lip sync," which is designed to cure this problem, but it's not widely implemented yet. Also, your display may have a specific "video game" setting mode. This disables video processing, so there is no latency introduced when using a game controller. But this can also result in less-than-optimal video quality for non-game video content.

Automatic Renewal Program: Your subscription will continue without interruption for as long as you wish, unless
you instruct us otherwise. Your subscription will automatically renew at the end of the term unless you authorize
cancellation. Each year, you'll receive a notice and you authorize that your credit/debit card will be charged the
annual subscription rate(s). You may cancel at any time during your subscription and receive a full refund on all
unsent issues. If your credit/debit card or other billing method can not be charged, we will bill you directly instead. Contact Customer Service